The scene at Sandy Hook Elementary School in Newtown, Conn., in Dec. 2012. / AP

by Larry Copeland, USA TODAY, USATODAY

by Larry Copeland, USA TODAY, USATODAY

The mentally troubled gunman in the Newtown massacre had obsessive behavior, changing his socks as many as 20 times a day, and his mother tried to manage her life around the bizarre quirks of her son, according to thousands of pages of documents released by Connecticut State Police on Friday.

But the release of the investigative files, which marks the end of the police investigation into the Dec. 14, 2012, mass shooting that killed 20 first-graders and six educators, offered only glimpses into what might have motivated Lanza, 20.

He had apparently displayed signs of the potential for violent behavior to at least one former teacher. The school massacre occurred just one day after his mother, Nancy Lanza, had returned from a two-night trip to New Hampshire, and came as she was mulling a move out of state, according to witnesses.

One of Lanza's former teachers told investigators that the shooter was anti-social and that he rarely interacted with other students.

"I remember giving creative writing assignments to students instructing them to write a page or two on whatever they wanted to talk about," she said. "Adam would write ten pages, obsessing about battles, destruction and war. In my years of experience, I have known (redacted) grade boys to talk about things like this, but Adam's level of violence was disturbing. I remember showing the writings to the Principal at the time. Adam's creative writing was so graphic that it could not be shared."

Lanza killed his mother at the home they shared. He then drove her car to the elementary school, went on a killing rampage, and then killed himself with a handgun as police arrived at the school.

The documents released Friday were heavily redacted to protect the names of children and witnesses and to withhold some of the most grisly details of the slayings.

One witness, a man who told police he'd known Nancy Lanza for about two years, said he was aware that Lanza "suffered from Asperger Syndrome. He never met Adam and had only been inside Nancy's residence once, approximately a year and a half ago. (He said) that Nancy never related any incidents in which Adam was violent with her. However, (he) felt that Nancy did a lot for Adam to assure that he was happy and appeased."

That witness, who last spoke with Nancy Lanza the evening before the shootings, told investigators that "over the past year Nancy had shared with him her plans to sell her home in Newtown and move to either Washington or North Carolina."

The witness said she had to postpone the sale of the house because "Nancy knew that she was not going to be able to effectively show/sell her home while Adam was living within. Her plan was to purchase (a Recreational Vehicle) to facilitate their move to either Washington State or North Carolina. During their trip, (the witness) related that Nancy would then sleep in a motel/hotel and Adam would sleep in the RV as he would not sleep in a motel/hotel. In this process, she could have Adam out of the house, they could effectuate their move and meanwhile, sell their house."

That witness showed police a text message from Dec. 10, 2012, in which Nancy Lanza said "Adam had 'bumped his head' 'really bad' and they were dealing with blood at 5:30 in the morning."

A former schoolmate of Lanza told police he often rode the bus with him and was in Tech Club with him in 2007 to 2008. The classmate "remembered that Lanza was quiet, and dressed neatly with a button down shirt with a pocket protector. (He) could not remember any odd behavior that stood out to him at the time. (He) did says Lanza was always fixing his hair, and carried a bag with cleaning supplies with him."

Another witness told police that Nancy "had taken him out of school because he was sensitive to sound and light." A nurse told investigators that Nancy Lanza had to do three loads of laundry a day because Adam Lanza obsessively changed his clothes, sometimes changing his socks 20 times a day.

On Dec. 11, 2012, Nancy Lanza checked into a hotel in Bretton Woods, N.H., checking out in the early afternoon on Dec. 13. A witness who who told police that he had lunch with her on Dec. 13, in Lebanon, N.H., said she told him, "Adam had some sort of autism."

"(The witness) said that Nancy Lanza told him she had no intentions of re-marrying and accepted the obligations of caring for Adam. Nancy said that she and Adam planned for her trip to New Hampshire. The trip was an experiment to allow Adam to stay at home alone for a few days."